Numerical Simulation of Lean Coal Combustion Based on Staged Plasma Ignition

Improving coal adaptability of plasma ignition systems is of significant importance for assisting power plants in energy conservation, emission reduction, and achieving the dual-carbon goals. To address issues such as unstable combustion and flameout encountered during the operation of existing staged plasma burners when igniting lean coal with low volatile content, this study employs a numerical simulation approach. First, a three-dimensional mesh model of the staged plasma burner is established, incorporating the Realizable k-ε turbulence model, the P1 radiation model, and a pulverized coal combustion model with Two-competing-rates model for volatile matter release and kinetics/diffusion-limited model for char combustion. Subsequently, mesh independence verification is conducted by comparing temperature parameter differences among models with low, medium, and high mesh densities to ensure the reliability of the selected mesh. Following this, the control variable method is applied to sequentially investigate the effects of three critical operational parameters—plasma power, primary air velocity, and pulverized coal concentration—on lean coal combustion process within the staged plasma burner. Finally, the operational parameters of the plasma burner are optimized to resolve ignition and combustion issues associated with lean coal. The results demonstrate that plasma power is the key factor affecting lean coal ignition. To achieve stable ignition and combustion of lean coal in the plasma burners, the plasma power should not be less than 150 kW. Primary air velocity affects the combustion temperature during the initial ignition stage, with an optimal range identified between 22 to 25 m/s. Pulverized coal concentration is a crucial factor for successful lean coal ignition; maintaining a relatively high concentration is necessary to ensure stable ignition and combustion, with a recommended concentration not lower than 0. 3 kg/kg. This research provides direct and important theoretical guidance and a practical basis for power plants to optimize the operational strategies of existing plasma burners, safely and economically utilize lean coal, reduce fuel costs, and lower carbon emissions. It holds positive implications for promoting fuel flexibility and facilitating the green, low-carbon transformation of coal-fired power plants.